A novel ternary nano-composite with a high photocatalyitic activity: Characterization, effect of calcination temperature and designing the experiments

Herein, we report the photocatalytic activity of a ternary NiO200/2h-CdS-CuO200/2h (calcination temperature: 200 degrees C) composite under Hg source irradiation in the presence of methylene blue (MB). The catalyst was characterized by XRD, SEM, FTIR, UV-Vis DRS, Cyclic voltammetry (CV) and Impedance spectroscopy (IS). Response surface methodology (RSM) was used for the modeling and optimization of the photocatalytic process. The reduction in the chemical oxygen demand (COD) of MB solution confirmed the mineralization of MB along with the color removal. The results showed that, calcination temperature and time have significant role on the photocatalytic activity of the prepared catalyst, so, higher calcination temperatures and also longer calcination time caused to decrease in the photocatalytic activity. Also, mixing of CuO-NiO before and after calcination process changed the photocatalytic activity of the ternary system. Mole ratio of the coupled catalyst had an important role on photocatalytic activity, and thus the best activity was obtained in mole ratio of 1:2:1 for the NiO200/2h CdS CuO200/2h catalyst. The best degradation extent was obtained in a run which included CMB: 3.91 mg L-1, dosage of catalyst 0.84 g L-1, pH: 3.6 during 65 min. Addition of scavengers to MB solution confirmed that e/h pairs have no direct role in MB photodegradation while OH radicals have the major role.